What causes necrotizing enterocolitis (NEC)?

The cause of NEC is not well known.1,2 In premature infants, the cause may be related to the immaturity of the child’s digestive system. NEC involves infection and inflammation in the child’s gut, which may stem from the growth of dangerous bacteria or the growth of bacteria in parts of the intestine where they do not usually live.1,2

Other possible causes of NEC that are related to having an immature gut include2:

Inability to digest food and pass it through, allowing a buildup of toxic substances

Inadequate blood circulation to the gut

Inability of the infant’s digestive system to keep out dangerous bacteria

Inadequate ability of the immature intestine to provide an adequate structural barrier to bacteria. This barrier usually matures in the unborn infant starting about week 26 (11 to 12 weeks before a full-term birth).

The inability of the immature gut to secrete its normal biochemical defenses

Because premature infants may lack any or all of these abilities, they may be more vulnerable to the types of inflammation that lead to NEC.2

Full-term infants who get NEC almost always do so because they are already sick or, in some cases, have a low body weight for their gestational age. They might have congenital heart disease or have had vascular bypass surgery, for example, possibly affecting the blood supply to the intestines.2

Full-term infants are usually diagnosed with NEC earlier than are premature infants (day 5 versus day 13 on average), possibly because they start feeding earlier. The condition is equally life threatening in premature and full-term infants.3

A recent NICHD-supported study found that a common type of medication, sometimes given to infants for acid reflux and called “H2-blockers,” was associated with a slight increase in the risk of NEC in preterm infants.4